OK, let's work through this together. We're starting with 810 and we're going to multiply it by 156, which means we add 810 to itself 156 times.
Step 1: 0 + 810 = 810
Step 2: 810 + 810 = 1620
Step 3: 1620 + 810 = 2430
Step 4: 2430 + 810 = 3240
Step 5: 3240 + 810 = 4050
Step 6: 4050 + 810 = 4860
Step 7: 4860 + 810 = 5670
Step 8: 5670 + 810 = 6480
Step 9: 6480 + 810 = 7290
Step 10: 7290 + 810 = 8100
Step 11: 8100 + 810 = 8910
Step 12: 8910 + 810 = 9720
Step 13: 9720 + 810 = 10530
Step 14: 10530 + 810 = 11340
Step 15: 11340 + 810 = 12150
Step 16: 12150 + 810 = 12960
Step 17: 12960 + 810 = 13770
Step 18: 13770 + 810 = 14580
Step 19: 14580 + 810 = 15390
Step 20: 15390 + 810 = 16200
Step 21: 16200 + 810 = 17010
Step 22: 17010 + 810 = 17820
Step 23: 17820 + 810 = 18630
Step 24: 18630 + 810 = 19440
Step 25: 19440 + 810 = 20250
Step 26: 20250 + 810 = 21060
Step 27: 21060 + 810 = 21870
Step 28: 21870 + 810 = 22680
Step 29: 22680 + 810 = 23490
Step 30: 23490 + 810 = 24300
Step 31: 24300 + 810 = 25110
Step 32: 25110 + 810 = 25920
Step 33: 25920 + 810 = 26730
Step 34: 26730 + 810 = 27540
Step 35: 27540 + 810 = 28350
Step 36: 28350 + 810 = 29160
Step 37: 29160 + 810 = 29970
Step 38: 29970 + 810 = 30780
Step 39: 30780 + 810 = 31590
Step 40: 31590 + 810 = 32400
Step 41: 32400 + 810 = 33210
Step 42: 33210 + 810 = 34020
Step 43: 34020 + 810 = 34830
Step 44: 34830 + 810 = 35640
Step 45: 35640 + 810 = 36450
Step 46: 36450 + 810 = 37260
Step 47: 37260 + 810 = 38070
Step 48: 38070 + 810 = 38880
Step 49: 38880 + 810 = 39690
Step 50: 39690 + 810 = 40500
Step 51: 40500 + 810 = 41310
Step 52: 41310 + 810 = 42120
Step 53: 42120 + 810 = 42930
Step 54: 42930 + 810 = 43740
Step 55: 43740 + 810 = 44550
Step 56: 44550 + 810 = 45360
Step 57: 45360 + 810 = 46170
Step 58: 46170 + 810 = 46980
Step 59: 46980 + 810 = 47790
Step 60: 47790 + 810 = 48600
Step 61: 48600 + 810 = 49410
Step 62: 49410 + 810 = 50220
Step 63: 50220 + 810 = 51030
Step 64: 51030 + 810 = 51840
Step 65: 51840 + 810 = 52650
Step 66: 52650 + 810 = 53460
Step 67: 53460 + 810 = 54270
Step 68: 54270 + 810 = 55080
Step 69: 55080 + 810 = 55890
Step 70: 55890 + 810 = 56700
Step 71: 56700 + 810 = 57510
Step 72: 57510 + 810 = 58320
Step 73: 58320 + 810 = 59130
Step 74: 59130 + 810 = 59940
Step 75: 59940 + 810 = 60750
Step 76: 60750 + 810 = 61560
Step 77: 61560 + 810 = 62370
Step 78: 62370 + 810 = 63180
Step 79: 63180 + 810 = 63990
Step 80: 63990 + 810 = 64800
Step 81: 64800 + 810 = 65610
Step 82: 65610 + 810 = 66420
Step 83: 66420 + 810 = 67230
Step 84: 67230 + 810 = 68040
Step 85: 68040 + 810 = 68850
Step 86: 68850 + 810 = 69660
Step 87: 69660 + 810 = 70470
Step 88: 70470 + 810 = 71280
Step 89: 71280 + 810 = 72090
Step 90: 72090 + 810 = 72900
Step 91: 72900 + 810 = 73710
Step 92: 73710 + 810 = 74520
Step 93: 74520 + 810 = 75330
Step 94: 75330 + 810 = 76140
Step 95: 76140 + 810 = 76950
Step 96: 76950 + 810 = 77760
Step 97: 77760 + 810 = 78570
Step 98: 78570 + 810 = 79380
Step 99: 79380 + 810 = 80190
Step 100: 80190 + 810 = 81000
Step 101: 81000 + 810 = 81810
Step 102: 81810 + 810 = 82620
Step 103: 82620 + 810 = 83430
Step 104: 83430 + 810 = 84240
Step 105: 84240 + 810 = 85050
Step 106: 85050 + 810 = 85860
Step 107: 85860 + 810 = 86670
Step 108: 86670 + 810 = 87480
Step 109: 87480 + 810 = 88290
Step 110: 88290 + 810 = 89100
Step 111: 89100 + 810 = 89910
Step 112: 89910 + 810 = 90720
Step 113: 90720 + 810 = 91530
Step 114: 91530 + 810 = 92340
Step 115: 92340 + 810 = 93150
Step 116: 93150 + 810 = 93960
Step 117: 93960 + 810 = 94770
Step 118: 94770 + 810 = 95580
Step 119: 95580 + 810 = 96390
Step 120: 96390 + 810 = 97200
Step 121: 97200 + 810 = 98010
Step 122: 98010 + 810 = 98820
Step 123: 98820 + 810 = 99630
Step 124: 99630 + 810 = 100440
Step 125: 100440 + 810 = 101250
Step 126: 101250 + 810 = 102060
Step 127: 102060 + 810 = 102870
Step 128: 102870 + 810 = 103680
Step 129: 103680 + 810 = 104490
Step 130: 104490 + 810 = 105300
Step 131: 105300 + 810 = 106110
Step 132: 106110 + 810 = 106920
Step 133: 106920 + 810 = 107730
Step 134: 107730 + 810 = 108540
Step 135: 108540 + 810 = 109350
Step 136: 109350 + 810 = 110160
Step 137: 110160 + 810 = 110970
Step 138: 110970 + 810 = 111780
Step 139: 111780 + 810 = 112590
Step 140: 112590 + 810 = 113400
Step 141: 113400 + 810 = 114210
Step 142: 114210 + 810 = 115020
Step 143: 115020 + 810 = 115830
Step 144: 115830 + 810 = 116640
Step 145: 116640 + 810 = 117450
Step 146: 117450 + 810 = 118260
Step 147: 118260 + 810 = 119070
Step 148: 119070 + 810 = 119880
Step 149: 119880 + 810 = 120690
Step 150: 120690 + 810 = 121500
Step 151: 121500 + 810 = 122310
Step 152: 122310 + 810 = 123120
Step 153: 123120 + 810 = 123930
Step 154: 123930 + 810 = 124740
Step 155: 124740 + 810 = 125550
Step 156: 125550 + 810 = 126360

So, 810*156 = 126360